Free Syrian Army fighters take their positions at the front line of Maaret al-Numan in Idlib province, Syria, on Feb. 26. / Hussein Malla, AP

by Jim Michaels, USA TODAY

by Jim Michaels, USA TODAY

WASHINGTON â?? If the United States decides to supply Syrian rebels with arms, it probably won't include the sophisticated weapons that would give them a decisive edge in their fight against government forces, analysts say.

Rebels are already being supplied with basic weapons and ammunition from Saudi Arabia and Qatar, but they lack sophisticated anti-tank and anti-aircraft missiles, which have the potential to turn the tide of war.

U.S. officials are reluctant to provide portable anti-aircraft missiles for fear they may fall in the wrong hands.

"We're never going to be hot on the idea of giving them shoulder-fired anti-aircraft missiles," said Jeffrey White, an analyst at the Washington Institute for Near East Policy and a former Defense Intelligence Agency official.

The Obama administration has said it has not made a decision on arming the rebels. "He is looking at a range of options, and he is not removing any option from the table," White House spokesman Jay Carney said of the president.

The administration provides "non-lethal" aid to rebel groups.

Arming rebels and other military options have gained urgency in the wake of a U.S. intelligence assessment that said the regime of Bashar Assad probably used chemical weapons. The administration had said such use would cross a "red line."

Republicans, such as Sen. John McCain of Arizona, have pushed the administration to take stronger action, such as arming rebels or creating a no-fly zone.

Sophisticated weapons are needed by the rebels because they would help ground Assad's aircraft and make it more difficult to maneuver tanks, taking away key regime advantages, said Mustafa Alani, director of national security for the Gulf Research Center in Geneva.

"The Syrian army relies on tanks and aircraft," Alani said. "This would change the whole situation on the ground."

Providing any arms to the rebels would be complex. The administration is worried about the presence of al-Qaeda-allied rebel groups, including the al-Nusra Front, a rebel group with Islamist ties.

Vetting those groups to determine how to distribute arms would be a complex task because the opposition is fractured and operates with little coordination or central leadership.

Rebel groups face spot shortages but generally have enough basic weapons and ammunition, which they get from captured Syrian army stocks or from Gulf countries, such as Saudi Arabia and Qatar.

Most of it is small arms, such as assault rifles, and rocket-propelled grenades. Alani said the Americans have discouraged the Saudis and Qataris from providing sophisticated weapons, such as shoulder-fired anti-air weapons.

White said there are options short of providing shoulder-fired missiles, including providing training on the use of heavy machine guns that could be used against armor and aircraft.

The Assad regime gets arms from Iran.

"The sources of weapons which are pouring into Syria are endless," said Ephraim Sneh, a military analyst and former deputy minister in Israel's Defense Ministry.

Even if it doesn't immediately change the balance of power, a decision to arm the rebels could be a demonstration of American commitment, suggesting the United States could increase shipments in the future, said Michael O'Hanlon, an analyst at Brookings Institution.

He said if the types of weapons are sharply limited, it could demonstrate the limits of American involvement.

"If we only supply the most minimal kind of equipment, you've created a new sense of restraint," O'Hanlon said.